I. Field of the Invention
The present invention relates to measurement systems and, in particular, to a tube-shaped bypass measurement section of absorption filters.
II. Description of the Prior Art
In activated carbon filtration units, it is desirable to examine the absorption level and the degree of saturation of the absorbent which is used in the filtration unit. This is done from time to time and without interrupting the function of the main carbon filtration units. Such requirements are especially important in nuclear engineering units.
The useful life of such activated charcoal filtration units depends on the amount of radioactive contaminants and other contaminants carried by the air to be filtered. If the concentration is high, the absorbent used (e.g. activated charcoal) must be replaced in time prior to exceeding the permissible limit with fresh absorbent. To determine the time for replacement in optimal fashion, bypass measurement sections are installed parallel to the main active charcoal absorption units. A partial airstream is diverted through the bypass section which features identical layer thickness and packing density. Samples are removed from the bypass section for examination. In this manner data is obtained concerning the status of separation efficiency and saturation of the absorbent in the main filtration unit.
The present state of the art, e.g. West German Pat. Nos. Gbm 712 66 75 and Gbm 741 72 94, exhibit the familiar tube-like filtration cartridges. These cartridges are charged with an absorbent that is the same as that employed by the activated carbon filtration unit, and the cartridge also has an absorbent layer thickness which is the same as the activated carbon filtration unit which is to be monitored. Such bypass measuring sections, or control filter sections, which generally bypass the main filtration unit in a parallel arrangement, usually are installed between the feed side and the discharge side.
The best known systems, represented by such bilaterally lockable bypass measuring sections, differ only with respect to the method of installation. Individual cartridges are either connected by means of gas-tight flanges or by screw pipe couplings; in either case, the layer thickness may be subdivided in several chambers. In some cases the test cartridges may even be exchanged, or removed, without disassembling the complete bypass section.
The bypass designs presently known to the art, mostly single or double sections, are not function specific; rather their design is governed by parameters requiring a special shape or necessary compliance with given installation needs, e.g. the avoidance of bulky components, such as ball valves or quarter bends, etc.
The inherent deficiencies of such devices have indeed been recognized but have heretofore not been remedied. In practical terms, given the presence of dangerous levels of radioactivity, during removal of the test cartridges from the measurement section, contamination by or dispersion of radioactive materials occurs. Controlled handling by means of adequate maintenance protection devices was heretofore not achievable, or only incompletely so, due to the lack of respective technical features.
A further disadvantage is inherent in designing the absorbent layer thickness in the bypass test cartridges in conformity with the bulk absorbent layer thickness of the main unit. It has been found that this is wrong. Because of the different packing density of the absorbent in the main filtration unit and in the test cartridge, the airflow velocities frequently are different. This results in wrong measurements with respect to saturation level and degree of separation as achieved by the activated charcoal in the test cartridges of the bypass sections.
A further disadvantage, which became recognized, is the absence of damper flaps and measurement devices which take readings directly at the bypass sections. Such devices allow for control of flow-through velocities of the air and make it possible to adjust these velocities to the respective values prevailing in the main absorption unit. A further disadvantage in the existing designs was the necessity of taking the total bypass section out of service, even if only one of the chambered sections needed to be recharged.